#include <iostream>
#include <math.h>
using namespace std;
class Point
{
    public:
    Point(int x,int y)
    :_ix(x)
    ,_iy(y)
    {}

    friend
    float destance(const Point &lhs,const Point &rhs);

    private:
    int _ix;
    int _iy;
};

//友元的普通类型函数形式
float destance(const Point &lhs,const Point &rhs)
{
    return sqrt(pow(lhs._ix - rhs._ix ,2)
                +pow(lhs._iy - rhs._iy,2));
}

void test0()
{
    Point pt(0,0);
    Point pt2(3,4);
    cout <<destance(pt,pt2) << endl;

}
int main()
{
    test0();
    return 0;
}